12.755 L06 Part I Previously: Metal speciation theory and biological cellular uptake theory Today: Connecting speciation and cellular uptake in the marine water column, and several generations of iron modeling Return to theme of introduction lecture: What are the processes controlling the distribution of hybrid type metals? How should they be parameterized in models? Do we have enough data yet?

Iron as a limiting nutrient in HNLC regions (Review of Iron Fertilization Experiments Boyd et al., 2007, Science) Purposeful (white crosses) and natural (red crosses) Fe enrichment studies have shown Fe limitation of phytoplankton growth.

Studies integrating iron modeling 1D – vertical profiles, no horizontal processes (Johnson 1997; Weber et al., 2007) 2D – GEOTRACES sections, horizontal processes 3D – GCM with iron (Fung, 2000; Archer and Johnson, Moore et al, 2002, 2004; Oschilles, Moore and Braucher 2008)

Fe:C determined using AOU: 2-13 mmol Fe mol-1 C, constant value of 5 not correct

Available iron database in 1999

Based on the Martin Carbon Power Law: Modified for production of dissolved iron, where Q is cellular quota (Fe:C ratio), with first order Fe scavenging with a “ligand protection term” (Fesoly)

“Ligand Protection” from scavenging is standard in models now

1D vs 2D Noble and Saito, preliminary data

Vertical fluxes require a source of metal Another clue in relative importance of vertical versus horizontal processes is M:P ratios If 1D processes dominate, Hybrid Metal:P correlations can be supported (metal and P are both subject to remineralization advection etc) If 2D processes dominate, unclear how Hybrid Metal:P are maintained. Point sources of metal likely do not have stoichiometric additions of P as well.

Generations of iron modeling Fung et al,. 2000

Parekh, Boyle, Fellows GBC From Parekh, Fellows, Boyle Box-model study, sensitivity testing of ligand parameters Parekh, Boyle, Fellows GBC

From Moore and Braucher 2008 BG

From Moore and Braucher 2008 BG

Colloidal = “dissolved” – soluble FeL is in all fractions Wu Boyle and Sunda, 2001

Further reading: Iron modeling studies Johnson 1997 Inez Y. Fung,1 Stephanie K. Meyn,2 Ina Tegen,3 Scott C. Doney,4 Jasmin G. John,1 and James K. B. Bishop5 GBC 1999 Archer and Johnson GBC 2000 Moore et al.., 2002, 2004 Parakh, Fellows, Boyle, GBC 2004 Weber, Volker Oschilies Burchard, BG 2007 Moore and Braucher Biogeosciences, 2008 Sedimentary and mineral dust sources of iron to the world oceans.

Societal Implications and Applications?